As we all know, silica sol can maintain suspension stability for a long time, but there are still many factors in the environment that can affect its stability. In particular, some matters should be paid attention to during storage, otherwise irreversible damage will occur. Let's take a look at the five major factors that affect the stability of silica sol.
Factors affecting stability 1. Freezing
Ordinary silica sol is an aqueous dispersion of nano-silicon dioxide. When the storage or use temperature of silica sol is too low, it will cause the silica sol to freeze. Once ordinary silica sol freezes, it will cause irreversible damage. Even if it melts again, flocculation and precipitation will occur in the silica sol. This is because when freezing occurs, the nano-silicon dioxide particles of the silica sol will be squeezed during the formation of ice crystals, causing them to agglomerate, thereby destroying the stability of the silica sol.
Factors affecting stability 2. Electrolyte
Ordinary silica sol is an aqueous dispersion of nano-silicon dioxide. The surface of the particles carries a negative charge and produces a repulsive effect, so no agglomeration occurs. This is the fundamental reason why the silica sol suspension system remains stable. Therefore, during use, ordinary silica sol cannot be added with multivalent salts, because the silicate on the surface of the silica sol will combine with multivalent metal ions to form insoluble salts, destroying its surface charge structure, thereby causing silica sol gelation, flocculation, etc.
Factors affecting stability 3: Cationic substances
Because the surface of silica sol nanoparticles is negatively charged, if cationic substances (such as cationic emulsifiers, multivalent metal ions, etc.) are added to the silica sol system, it will cause silica sol flocculation and irreversible scrap.
Factors affecting stability 4: Organic macromolecules
If water-soluble organic macromolecules are added to ordinary aqueous silica sol systems, the silica sol will gradually thicken or eventually gel. This is because organic macromolecules with excessive molecular weight will adsorb on the surface of silica sol nanoparticles, cover their surface charges, and weaken the charge repulsion between silica sol particles, thereby causing silica sol gelation.
Factors affecting stability 5. Open container
When using silica sol, if the container is open for a long time, the surface water will evaporate and silicon dioxide crystals (fine needles or sand particles) will precipitate. This phenomenon generally does not affect the stability of silica sol, but it may affect its use. When using it, it is necessary to use a very fine filter cloth to filter out these solid precipitates.